Proteins (Nonenzymatic): Functions & Cell Signaling

Question 1

Cell adhesion molecules (CAM)

Answer 1

allow cells to bind other cells or surfaces

include cadherins, integrins, and selectins

Question 2

Cadherins

Answer 2

calcium-dependent glycoproteins that hold similar cells together
(two cells of same or similar type using calcium)

Question 3

integrins

Answer 3

have two membrane spanning chains
permit cells to adhere to proteins in the ECM
some have signaling capabilities
(one cell to proteins in the ECM)

Question 4

Selectins

Answer 4

allow cells to adhere to carbs on the surfaces of other cells; most commonly used in the immune system
(one cell to carbohydrates, usually on the surface of other cells)

Question 5

variable region of immunoglobulins

Answer 5

responsible for antigen binding

Question 6

antibody structure

Answer 6

two identical heavy chains and two identical light chains held together by disulfide linkages and noncovalent interactions

Question 7

Structural proteins

Answer 7

compose the cytoskeleton, anchoring proteins, and much of the ECM; generally fibrous in nature
include collagen, elastin, keratin, actin, and tubulin

Question 8

Motor proteins

Answer 8

involved in muscle contraction, vesicle movement, and cell motility

have one or more heads capable of force generation through a conformational change and catalytic activity, acting as an ATPase to power movement

include myosin, kinesin, and dyenin

Question 9

3 main types of ion channels

Answer 9

ungated, voltage gated, ligand gated

Question 10

ungated channels

Answer 10

always open

Question 11

voltage gated channels

Answer 11

open within a range of membrane potentials

Question 12

ligand gated channels

Answer 12

open in the presence of a specific binding substance (hormone or neurotransmitter)

Question 13

enzyme linked receptors

Answer 13

participate in cell signaling through extracellular ligand binding and initiation of second messenger cascades

Question 14

G protein coupled receptors

Answer 14

have membrane bound protein associated with a trimeric G protein and initiate second messenger systems

Question 15

GPCR signal cascade

Answer 15

1. ligand binding engages the G protein
2. GDP replaced with GTP; alpha subunit dissociates from the beta and gamma subunits
3. activated alpha subunit alters the activity of adenylate cyclase of phospholipase C
4. GTP is dephosphorylated to GDP; the alpha subunit rebinds to the beta and gamma subunits